According to the Portfolio Grader database this week, the Metals and Mining, Computer and Personal Electronics, Energy Services, Oil and Gas, and Marine sectors are at the bottom.

The Metals and Mining sector is dragging, with 77% of its stocks (72 out of 93) rated a “sell”. Out of the Metals and Mining stocks, Cliffs Natural Resources (NYSE:CLF), Walter Energy Inc. (NYSE:WLT), and Thompson Creek Metals (NYSE:TC) finished near the bottom. Cliffs Natural Resources has a score of F while Walter Energy Inc. and Thompson Creek Metals rated F and F. Walter Energy Inc. is the worst stock in its sector, with the company’s share price falling 79.3% in the last 12 months.

With 62% of its stocks (13 out of 21) rated “sell,” the Computer and Personal Electronics sector is struggling this week. Among Computer and Personal Electronics stocks, Diebold (NYSE:DBD), QLogic (NASDAQ:QLGC), and Hewlett-Packard (NYSE:HPQ) finished near the bottom. Diebold is currently rated F. QLogic and Hewlett-Packard are rated F and F. Hewlett-Packard is performing worst overall in the sector, with a 1.6% decline over the last 12 months.

The Energy Services sector is trailing behind others this week, with 61% of its stocks (34 out of 56) rated a “sell”. Finishing near the bottom this week are Gulfmark Offshore (NYSE:GLF), Key Energy Services (NYSE:KEG), and Nabors Industries (NYSE:NBR) among the Energy Services stocks. Gulfmark Offshore has a score of F while Key Energy Services and Nabors Industries rated F and F. Overall, Key Energy Services is the poorest performer in this sector. Its share price has dropped 55.8% in the last 12 months.

The Oil and Gas sector looks weak, with 60% of its stocks (122 out of 204) rated a “sell”. Among Oil and Gas stocks, Enerplus (NYSE:ERF), Swift Energy (NYSE:SFY), and Newfield Exploration (NYSE:NFX) lingered near the bottom. Enerplus has a score of F while Swift Energy and Newfield Exploration rated F and F. The worst performer in this sector is Swift Energy, which saw its price sink 53.2% in the last 12 months.

The Marine sector is lagging this week with 57% of its stocks (4 out of 7) rated a “sell”. Diana Shipping (NYSE:DSX) andNavios Maritime Partners (NYSE:NMM) are dragging down the sector overall, each earning a high score of D.DryShips (NASDAQ:DRYS) currently ranks F.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.